feasibility of HTML5 web on platforms

Would be very interested to see your point of view, particularly with regard to the direction and feasibility of HTML5 web and/or native web apps on both these platforms. Am especially interested in the (at least) theory of one fits all approach for not just operating system (iOS / Android / etc) and the arguable expectation of OS specific customisations (e.g native date pickers), but also form-factor, both smartphone v tablet, but desktop / pc inclusion too. Also interested in your view of native / hybrid web apps (e.g via PhoneGap). Of course it depends on the app.
Anyway, an interesting subject area.
Cheers!

Well, it certainly is possible to write one web app and then use it on both iOS and Android without modification, as long as you use standard HTML5. Soon it will be possible to use the same web app as a standalone app on Windows Phone 7 and Windows 8 too. This convergence is the way app development is heading in my view.